Never had this happen before

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Had a guy call us today to weld a ten thousand gallon alum. diesel tank. He bought this tank from a guy and my customer never tested if before putting diesel in it. Well today they put diesel in it and what a surprise, leaking around a bun that was alum wire welded by a blind guy. I fired up the TB and high frq box and tried to weld the cracks. About 10 mins into the job, desicded to stop. It was -2 out and i had my welder turned up so high, i was melting the cup. I never would of thought i would see the day that an alum tank would be cold enough to weld.Suppose to be 50 out Friday, told the customer that i would come back and weld it Friday afternoon. Not really sure what else i could of done. I was going to try to heat with a torch, but i was thinking that it wouldn't help. Tank is 3/16 thick, bun i am guessing 1/2 wall. If i remember i will snap some pictures before we start on it Friday.
Reply:You can preheat alloy carefully.....(and it does help)I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:It was so freaking cold today, that preheating would not of helped.
Reply:helium gas mix???  expensive but works on thick sections.
Reply:Yes preheating helps.  Especially when the weather and the material are cold!  The best laid schemes ... Gang oft agley ...
Reply:10,000 gallon tank, and maybe 1/2" thick?  That's a lot of HEAT SINK.  I wouldn't even attempt to TIG weld it.  MIG is the way to go for that baby, and then after lots of preheat.Good Luck.
Reply:pawelder,TIG could work. The Miller TIG parameter calculator suggests 150-180 amps, 3/32 tungsten, and 3/32 filler rod for a 3/16 fillet joint  That's really not that outrageous.Miller's calculator suggests 250 amps and 1/8 tungsten and 1/8 filler for a 3/8 lap joint, so that is rising up pretty quickly amps-wise as the material gets thicker.Full 1/2 inch thick aluminum lap joint and Miller suggests 300 amps.  That's getting hot now!But yes I fully agree that the tank was a big COLD heatsink and that preheat was called for.AG, you -are- being careful welding a fuel tank right?    The best laid schemes ... Gang oft agley ...
Reply:Yah we weld on fuel tanks all the time. Deisel is not as scary as gas....
Reply:[QUOTE=MoonRise;262213]pawelder,TIG could work. The one key word is "could".  Take forever though.  That thickness, I'd definitely MIG weld it.  Being paid by the hour, TIG could be profitable. However, that's just MHO.
Reply:pawelder,Oh, I agree again. TIG would be a s-l-o-w way of doing it.Then again, one of the Mass welders  here (Tozzi?) TIG welded a stainless steel metal roof on a convention center.    But that was sheetmetal.    The best laid schemes ... Gang oft agley ...
Reply:Here is the reason that i didn't mig it. With tig i can really make sure to burn out the nasty dirty stuff that i couldn't get cleaned with a brush or couldn't get a sandblaster to it. Also, i am not really sure what the base material is, so don't know what wire to wire with. 4043 or 5356. Also, I have better luck getting a tig weld to seal better then wire. Share your input??
Reply:If I bought a NEW 10,000 Gallon ALUMINUM fuel tank and it leaked?    I feel sorry for the first person from that company I make contact with!Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:did you wash or purge the tank? I got a call to do the same kind of repair. Just wondering the safe way to do it
Reply:personally i agree with your decision Ag, waiting till you can get decent heat for proper weld would be best. My only suggestion is you mentioned all the contaminents in your weld you are rewelding and that you were brushing them out. Get a skillsaw with a carbide blade(or really any wood cutting blade will work) and cut all that dirty sh** out of there. Well cuts a bad term, more like shave the top layers off to nice shiny Alum. Brushing only gets you so far.
Reply:Originally Posted by cogaxpersonally i agree with your decision Ag, waiting till you can get decent heat for proper weld would be best. My only suggestion is you mentioned all the contaminents in your weld you are rewelding and that you were brushing them out. Get a skillsaw with a carbide blade(or really any wood cutting blade will work) and cut all that dirty sh** out of there. Well cuts a bad term, more like shave the top layers off to nice shiny Alum. Brushing only gets you so far.